As discussed by Cotton and Wilkinson, pp. 216-217, Advanced Inorganic Chemistry (1967), T is formed continuously in the upper atmosphere of the earth by cosmic ray-induced nuclear reactions. Accordingly, fast neutrons derived from cosmic ray reactions can produce T by the reaction EQU .sup.14 N(n, .sup.3 H).sup.12 C
and T is radioactive with a half-life of about 12.4 years. Also, T is made artificially in nuclear reactors, for instance, by the bombardment of lithium with thermal neutrons to form tritium with the emission of alpha particles, according to the formula EQU .sup.6 Li(n, .alpha.).sup.3 H
and is commercially available.
As also discussed by Cotton and Wilkinson, D as D.sub.2 O is separated from H.sub.2 O by fractional distillation or electrolysis and by utilization of very small differences in the free energies of the H and D forms of different compounds. D.sub.2 O is commercially available and used as a moderator in nuclear reactors, and also used widely in the study of reaction mechanisms and of spectroscopic mechanisms.
More specifically, as is mentioned in many of the patents cited below, T can be found in nuclear fuel reprocessing plants, waste streams from military operations connected with nuclear weapons programs, and nuclear power reactors that employ D.sub.2 O as a moderator and/or coolant. Presently, T is removed from H.sub.2 O and D.sub.2 O by various gaseous hydrogen separation techniques, such as distillation of H.sub.2 O, cryogenic distillation of gaseous hydrogen, and the like. Additionally, T.sub.2 O can be concentrated from DTO contaminated D.sub.2 O by various processes such as vacuum distillation or electrolytic cascade (several stages of water electrolysis), but such processes are of limited use because of the high toxicity of T.sub.2 O, the low separation factor for distillation, and the high power consumption for the electrolizers. Thus, it is more practical either to convert DTO into the elemental T such as by electrolysis, or to extract T from the water by catalytic exchange with a deuterium stream. Then, the much less toxic elemental T can be enriched by known processes such as cryogenic distillation.
Of interest, each of Canadian Patent No. 1,137,025 issued Dec. 7, 1982 to Dombra, U.S. Pat. No. 4,190,515 issued Feb. 26, 1980 to Butler and Hammerli, and U.S. Pat. No. 4,228,034 issued Oct. 14, 1980 to Butler, Rolston, den Hartog, Molson, and Goodale (all three patents assigned to Atomic Energy of Canada Limited) disclose processes and/or apparatuses for the removal of D and/or T from water.
Also of interest, Japanese Patent No. 61028426 published Feb. 8, 1986 to Masakazu (assigned to Japan Atom Energy Research Institute) discloses a process to concentrate and to recover T as T.sub.2 or D as D.sub.2 from a gaseous mixture consisting of H.sub.2, HT, and T.sub.2 or of H.sub.2, HD, or D.sub.2, respectively, by a system including an isotope separation column and a catalytic reaction column. Additionally, Japanese Patent No. 8026703 published Jan. 30, 1996 to Masaaki (assigned to Permelec Electrode Limited) discloses a process to obtain D by electrolyzing an electrolyte, as water containing D in an electrolytic cell divided into an anode compartment and a cathode compartment, with an ion exchange membrane. According to Masaaki, the process does not cause problems due to explosions from hydrogen and oxygen since they are mixed and recombined into water.
Of background interest with respect to Ru complexes employed in the present invention, McHatton and Anson, "Electrochemical Behavior of Ru(trpy)(bpy)(OH.sub.2).sup.3+ in Aqueous Solution and When Incorporated in Nafion Coatings", Vol. 23, Inorganic Chemistry, pp. 3935-3942 (1984) describe that polypyridyl complexes of Ru that contain at least one water ligand, when in a Nafion (NAFION 117.RTM. is a fluorinated polymer sold by DuPont and having the formula ##STR1##
where x and y are the number of repeating monomer units) coating on a graphite electrode can be oxidized to the corresponding oxo complexes of Ru.sup.IV. Also background, Moss, Argazzi, Bignozzi, and Meyer, "Electropolymerization of Molecular Assemblies", Vol. 36, Inorganic Chemistry, pp. 762-763 (1997) describe that electropolymerization of appropriately derivatized metal complexes on conducting substrates leads to electroactive thin films, and one approach was reduction of vinyl-containing polypyridyl complexes such as Ru(vbpy).sub.3.sup.2+, where vbpy is 4-methyl-4'-vinyl-2,2'-bipyrindine.
Additionally, Roecker (a coworker at the University of North Carolina of one of the inventors (Meyer) of the subject invention) and Meyer had investigated the kinetics and mechanism of the oxidation of a number of alcohol organic substrates by a bipyridine-pyridine ruthenium.sup.IV oxo complex, namely [Ru.sup.IV (bpy).sub.2 (py)(O)](ClO.sub.4).sub.2 in order to provide [Ru.sup.IV (bpy).sub.2 (py)(O)].sup.2+, for comparing the protio form of the alcohol organic substrate to the deuterio form of the organic substrate. Their work revealed large, primary deuterium kinetic isotope effects for benzyl alcohol, namely for PhCH.sub.2 OH compared to PhCD.sub.2 OH. See, Roecker and Meyer, "Hydride Transfer in the Oxidation of Alcohols by [(bpy).sub.2 (py)Ru(O)].sup.2+. A k.sub.H /k.sub.D Kinetic Isotope Effect of 50", Vol. 109, Journal of the American Chemical Society, No. 3, pp. 746-754 (1987).
For instance, Roecker and Meyer found that oxidation of benzyl alcohol (as the organic substrate) by the bipyridine-pyridine ruthenium.sup.IV oxo complex, as shown by the equation EQU [Ru.sup.IV (bpy).sub.2 (py)(O)].sup.2+ +PhCH.sub.2 OH.fwdarw.[Ru.sup.II (bpy).sub.2 (py)(OH.sub.2)].sup.2+ +PhCHO
displayed a deuterium kinetic isotope effect that exhibited a ratio of rate constants of EQU k(C--H)/k(C--D)=50
while displaying no significant H.sub.2 O/D.sub.2 O solvent isotope effect.
However, Roecker and Meyer in "Hydride Transfer . . . " failed to recognize any use for their observed kinetic isotope effect with the bipyridine-pyridine ruthenium.sup.IV oxo complex. In contrast, the present inventors have surprisingly discovered a method for hydrogen isotope separation by employing ruthenium oxo complexes for concentration and separation of hydrogen isotope contamination from contaminated water.